Voice over Internet Protocol (VoIP) has two transmission manners: direct connection and transit.
The direct connection is that a user equipment performs point to point (P2P) data transmission with another user equipment. The advantage of the direct connection is simplicity and high efficiency, and the disadvantage of the direct connection is weak stability and controllability. The transit is to add a transit server between two user equipment that are in a call, and a data stream needs to be transmitted to a peer end by using the transit server. The advantage of the transit is stability and controllability, and the disadvantage of the transit is a need for support by a server resource and a bandwidth resource.
In view of the above, the two transmission manners: direct connection and transit both have respective advantages and disadvantages. Directly using either transmission manner cannot ensure that the link quality of the VoIP is always stable and reliable.